Hitherto, for example, air cylinders as an air pressure actuator have been widely used for a variety of automatic machines and have a structure where a piston with a fixed rod is reciprocally moved in a pressure chamber by supplying and exhausting compressed air. In general, compressed air is supplied and exhausted to/from such an air cylinder through a switching valve.
In such an air cylinder, for a work stroke, a pressing stroke which is one of the two strokes of the piston moving reciprocally, a large driving force is necessary because an external load is applied to the rod. On the other hand, for a return stroke, by which the piston returns to the initial position, a driving force is smaller than that for the work stroke because the external load is not applied to the rod. The driving force depends on the pressure of the compressed air supplied to the pressure chamber. Therefore, in consideration of energy conservation and reduction in the running cost by saving air consumption, the pressure of compressed air for the return stroke is desirably set lower than that for work stroke.
To solve such a problem, arrangement of decompression valves 6, 125 on a main flow path connected with the pressure acting chambers of a cylinder tube is offered in PTL 1. However, it is necessary to provide the decompression valves 6, 125 in addition to switching valves for switching supply and exhaust air to/from the respective pressure acting chambers of the cylinder tube, causing problems of complication and a large size of equipment and a high initial cost.